In a known controlled-combustion fireplace, sold under the trade mark "BAXI", ducting which opens below the hearth extends away from the fireplace to an inlet opening which permits the ingress of fresh air from outside the room being heated by the fireplace. Control of this fresh air flow is effected by a control vent in the ducting, below the fireplace.
With this form of construction, the fresh air is intended solely for combustion purposes and flows straight through the fireplace at a rate depending upon the size of the opening provided by the control vent. The heat derived from such a fireplace is transferred mainly by radiation.
One known convected air fireplace, sold under the trade mark "JET MASTER", in which an attempt is made to solve this problem, comprises an inner casing, for accommodating a fire and having an open front, a rear panel, an open top panel, a bottom panel and two side panels; outer casing means enclosing at least one first air space below the inner casing and passage means for air extending upwardly from the or each first air space along at least one side panel of the inner casing; front air inlet means opening into the first air space, at the front of the fireplace; and front air outlet means communicatively connected to the passage means and opening at the front of the fireplace, above the level of the front air inlet means.
Convected air which is drawn in from the room to be heated through the front air inlet means at the bottom of the fireplace flows back into the room through the front air outlet means at the top of the fireplace. With this form of fireplace, the heat derived from the fire is greatly increased in that it depends not only on radiation, but also on the heat carried by convected air currents. However, warm air is drawn from the room to support combustion and this causes cold draughts to flow towards the fireplace from doorways, windows and other openings in the room, thereby cooling the backs of people sitting in front of the fireplace and it has been found that the induced convection currents concentrate this flow of cold fresh air along the floor of the room where it is most uncomfortable to the people sitting in front of the fireplace.